The objectives are to study energy expenditure and metabolic processes concerned with generation and expenditure of energy in renal failure. The purpose is to gain knowledge concerning potential causes of and methods for treating wasting and malnutrition in uremia. Four experiments are proposed: 1) assess energy expenditure and requirements in clinically stable uremic patients not dialyzed or undergoing maintenance dialysis and normal volunteers who will be fed different energy intakes during short-term (2-day) or long-term (76-day) studies in a metabolic research unit; 2) the metabolic response to brief (25-hour) starvation, a common event in uremia; 3) energy expenditure and requirements in patients with chronic renal failure and superimposed catabolic stress or in patients with acute renal failure who are administered varying levels of energy intake; and 4) during hemodialysis, the effects on the catabolic status of the patient of using dialysate containing no glucose or high (450 mg/dl) levels of glucose or containing acetate vs. bicarbonate. Procedures to be employed include energy expenditure (indirect calorimetry), nitrogen and potassium balances, anthropometric and biochemical indicators of nutritional status, blood levels of energy fuels (amino acids, glucose, lactate, pyruvate, triglycerides, fatty acids, glycerol, beta-hydroxybutyrate and acetoacetate), insulin and glucagon. In selected patients glucose and alanine turnover will be measured and muscle tissue will be biopsied and analyzed for high energy compounds, substrates and enzymes involved with energy production, and mitochondrial oxygen consumption and creatine phosphate production. Relationships will be assessed between parameters of clinical and nutritional status, energy expenditure, energy requirements, and the metabolic response to high energy intakes, starvation and glucose-free dialysate. Urea kinetics during hemodialysis will be investigated. Methods for estimating net protein catabolic rate from pre- and postdialysis serum urea, body wieght, and dialyzer kinetics will be evaluated.